X-ray fluorescence (XRF) marking is a technique used to detect and possibly quantify chemical material elements and/or composition constituents which can serve for marking an object. The parameters/identity of an object can then be identified based on the detected materials.
In the following, X-ray fluorescence (XRF) is used to refer to the emission of characteristic “secondary” (or fluorescent) X-rays from a material that has been excited by primary X-rays or gamma rays radiation. The term fluorescence refers to absorption of radiation of a specific energy resulting in the re-emission of radiation of a different energy (typically lower). The X-ray fluorescence (XRF) phenomenon is based on the fact that when materials are exposed to short-wavelength X-rays or gamma rays, they may expel electrons from inner orbitals of the atom, which thus cause electrons in higher orbitals to “fall” into the lower/inner orbital, and, in the process, release photons with energy equal to the energy difference between the two orbitals involved. Different chemical elements have electronic orbitals/shells of different characteristic energies, and therefore the spectral profile of an XRF response from an object/material is indicative of the chemical elements and possibly of the amount of each element included in the material/object.
Counterfeiting and supply chain diversion of materials are phenomena that impact many fields. Many materials of inferior quality, including but not limited to raw materials, electronics, polymers and pharmaceuticals are counterfeited by unscrupulous manufacturers and enter the supply chain, often by copying labeling associated with “brand” companies. To this end there are various techniques known in the art which utilize XRF marking to identify object/materials and determine their source/manufacturer/owner and/or various parameter, thereby enabling to discern between the original materials/goods and counterfeit materials/goods. Since chemical makeup of the original and counterfeited materials may be similar, some techniques utilize additive XRF markers (such as compositions of materials having a specific a-priori known XRF signature), which are specifically added to the object to enable identification of the object and/or certain parameters thereof, such as its source.
For example U.S. Pat. No. 8,590,800 discloses a method of authenticating and/or identifying an article containing a chemical marking agent, which is substantially inseparably enclosed in a marker as a carrier and contains selected chemical elements and/or compounds in the form of marker elements, in concentrations based on a predetermined encryption code, which method comprises the steps of: i) qualitatively and/or quantitatively identifying the marker elements of the chemical marking agent, and ii) comparing the values identified in step (i) with the predetermined encryption code.
U.S. Pat. No. 8,864,038 discloses a material tracing technique for encoding information in a material. The technique includes storing information to be encoded in the material, generating a number based on the information, determining an amount of at least one tracer to be incorporated into the material corresponding to the number, and incorporating the determined amount of the at least one tracer into the material. Decoding information encoded in the material includes measuring an amount of the at least one tracer, in some embodiments after tracer activation, determining a number corresponding to the measured at least one tracer, and decoding the number to obtain information associated with the material.
U.S. Pat. No. 8,158,432 discloses a system for marking a fluid by a marker, the fluid flowing from a source to a destination, the system including a sensor for determining a value of a fluid property and a fluid flow controller for admitting a selected amount of the marker to the fluid, wherein the selected amount is determined according to the fluid value and a predetermined concentration of the marker in the fluid in the destination.